What we've done so far:

Wednesday, November 2
Friday, November 4
Monday, November 7
Wednesday, November 9
Friday, November 11 - Remembrance Day
Monday, November 14
Wednesday, November 16
Friday, November 18
Monday, November 21
Wednesday, November 23
Friday, November 25
Monday, November 28
Wednesday, November 30
 

Wednesday, November 2
For 9.3 Lattice Energy of Ionic Compounds, concepts are important here: not numbers.  Know about lattice energies being positive, and be able to compare lattices based on the charges and sizes of the ions involved.

Lattice Energy (E) = k Q1Q2
                                  r

End of chapter exercises: 80, 85, 90, 92, 114, 120

Now that we have a firm grasp on the skill of drawing Lewis Diagrams, we can proceed onwards.
Lewis diagrams tell us about the valence electrons in a molecule, and about the connectivity.

The Valence Shell Electron Pair Repulsion Model will allow us to predict the shapes of many molecules. 10.1 Molecular Geometry

The word Pair is rather misleading in the  VSEPR model.  I refer to "electron Groups" (or E.G.) to make it absolutely clear in deriving the molecular shape. An E.G. can be a single bond, a double bond, a triple bond, or a lone pair.

After a little demo with people and ropes - we tried the first simplest case of 2 E.G. using my steps.

Then, a real demo about silane!

Friday, November 4
Onto 3 E.G. and 4 E. G. and considering lone pairs on central atoms!

SKILL: You should be able to draw all of the basic shapes mentioned in class

Remember! This is an extremely important SKILL


Monday, November 7
I finished the rest of the shapes you will need to know.
Exercises from Chang: 7, 10, 12, 14 (except CdCl42-)

You got back your tests - make sure you look at the breakdown on D2L!

Wednesday, November 9
10.2 Dipole Moments
Polar bonds can be examined to determine molecular polarity.  Add up the dipoles, like vectors
Some molecules have polar bonds, but do not have an overall dipole moment.
Now we can relate the new skill of VSEPR  back to the dipole moment of a molecule.
SKILL: Since we now know how to determine the shape of a molecule, we can figure out its dipole moment.

Clickers for VSEPR.  Click here for the document. 

Friday, November 11
No class

Monday, November 14
The next goal in lectures: relate our understanding of atomic structure to our understanding of molecular structure.
Note: Chang covers MORE material than Chemistry 201 students need to know, so make sure you come to lecture or get notes, because this is the only way you will know what is important here!

Clickers for Bond Orders.  Click here for the document.


Wednesday, November 16
More MO theory...
Important guidelines:

1.  overlap must happen - atoms need to be close enough
2.  orbitals must have similar energies
3.  orbitals must have similar/compatible symmetry

We can use the M.O. model for any molecule, but for this course we will only look at simple homonuclear diatomics.  We drew the M.O. diagram for oxygen.  Click here for the M.O. energy level diagram for O2.  Electrons are added according to the rules we already know for atomic energy level diagrams. 

Drawing orbital overlaps for p orbitals...
...some more bond order calculations including O2- and F2 for homework!

Clickers for MO theory.  Click here for the document.

Friday, November 18
Clickers for MO theory.  Click here for the document.

Remember a pi bond is not as strong as a sigma bond - this affects the reactivity!...more later on this

The M.O. diagram tells us information about a compound's reactivity: Highest Occupied Molecular Orbital reacts with electrophiles, Lowest Unoccupied Molecular Orbital reacts with nucleophiles.
Exercises: 46, 47, 48, 52, 58
 
Now onto a DIFFERENT model: 10.3 Valence Bond Theory

The atomic orbitals we learned earlier will not give us the geometries that we predict from VSEPR!  How do we rationalize this?  We use the idea of hybridisation or "mixing" of orbitals to give us hybrid orbitals that do have the appropriate orientations.


We made several types of hybrids before the demo...

Monday, November 21

Clickers for hybrids.  Click here for the document.

Methane and Ammonia Examples: 4 sp3 orbitals in a tetrahedral arrangement
BF3:
3 sp2 orbitals in a trigonal planar arrangement with a leftover p orbital. 
Sometimes, the p orbitals left over are empty and very reactive. 

Definition: single bond - sigma bond - located directly between the atoms

One more example of 3 sp2 orbitals in a trigonal planar arrangement with a leftover p orbital involved in a pi bond.

Definition: pi bond - located above and below the plane of the atoms
Double bond is sigma + pi = 4 electrons total (2 sticks)

Answers to homework: click
here.

Wednesday, November 23

Clickers for hybrids.  Click here for the document.

Triple bond - sigma + 2 pi = 6 electrons total (3 sticks)

The last two types of hybridisation we will consider:

5 sp3d ( or dsp3) orbitals in a trigonal bipyramidal arrangement
6 sp3d2 (or d2sp3) orbitals in an octahedral arrangement

Remember, hybridisation is a model - the atoms don't really hybridise! Why do we bother?  Because the model is simple, but extremely useful in predicting bonding and reactivity for many molecules.
 
We learned about the sigma-framework of molecules that have resonance structures, and that they have delocalised pi bonding (10.8 Delocalised Molecular Orbitals)
An introduction to Line Drawings - look to D2L.
Exercises: 26, 34, 36, 38, 40, 42, 44 and 63, 72, 76 (except e), 80 (expect CdBr2), 82, 88


Answers to homework: click here.

Friday, November 25

Clickers for hybrids and line drawings.  Click here for the document.

Kinetics!

How fast can a reaction go?
Speed will depend on:
13.1 The Rate of a Reaction: Rate is another word for speed - how a quantity (concentration) changes as time passes.
The rate of a reaction can be represented mathematically - 13.2 The Rate Law
For the generic reaction: Rate = k[A]x[B]y
x is the order with respect to A and is not related to a
y is the order with respect to B and is not related to b
k is called the rate constant: for a given reaction at a given temperature.
x, y, & k come from experiment, so we need to leave them as algebra until we know some experimental details

Monday, November 28


Homework - Average rates example - for answers, click here

Determining the Form of the Rate Law requires the Method of Initial Rates.
SKILL: My steps overhead allowed us to work through two examples.  (See link on my main page for kinetics notes and these steps).
Homework for Initial Rates - for answers, click here
Remember that you can work out the units of k if you know the overall order.
The rate law used so far is also known as the differential rate law since it involves a derivative. 
The Integrated Rate Law allows the rate law to be converted to an equation where concentration depends on time.  This is a much simpler experimental issue. 
This is a good time to remember about logarithms. See Appendix in your text!

Exercises: 2, 8, 16, 18

What if a reaction has more than one reactant?
More complicated math: simplified by an experiment which holds all but one of the reactants at a large concentration (therefore relatively constant) as in Expt 5.

SKILL: The integrated rate laws can be used to determine the rate law for a reaction if concentration and time data are provided. See Expt 5!

Once the form of the integrated rate law is known, then for any time, [A] is known, or vice versa.

So: another important piece of information can be deduced - the half life of a reaction. The half life is the time required for the reaction to be 50% completed or to have 50% remaining (glass half-full/half-empty).  More next day...


Wednesday, November 30

Similar calculations can be used any time the extent of reaction is known: % reacted or complete or % remaining.
For my summary table, click here.

SKILL: calculate concentration or time based on the integrated rate laws. 

Exercises: 28, 29, 30. 
Homework for Integrated Rates - for answers, click here

In general, for kinetics problems:
How do reactions happen? Collision model.
Use
the Arrhenius equation to see how k depends on T.
SKILL: calculate activation energy from rate constants at different temperatures. Exercises: 34, 38, 40, 42 and a Homework problem,
for answers, click here

What happens after the molecules collide? For the old exam question I used as an example,
click here
For the reaction to occur, they will stick together in an activated complex : Intermediates can form